Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
ASSETS
Total securities available-for-sale	$ 588,488	$ 509,425
Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	270,248	234,751
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	94,604	63,774
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	46,389	48,669
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	39,920	39,052
Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale	128,313	114,264
Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	9,014	8,915
Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale	588,488	509,425
Trading securities held in a Rabbi Trust	3,117	2,864
Total securities	591,605	512,289
Total Assets	605,979	526,106
LIABILITIES
Total Liabilities	14,109	13,647
Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	270,248	234,751
Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	94,604	63,774
Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	46,389	48,669
Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	39,920	39,052
Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale	128,313	114,264
Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	9,014	8,915
Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets	14,082	13,698
LIABILITIES
Derivative financial liabilities	14,050	13,647
Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets	292	85
Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets	0	34
LIABILITIES
Derivative financial liabilities	59
Level 1 [Member] | Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale	179	202
Trading securities held in a Rabbi Trust	3,117	2,864
Total securities	3,296	3,066
Total Assets	3,296	3,066
LIABILITIES
Total Liabilities	0
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	179	202
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets
LIABILITIES
Derivative financial liabilities
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets	0
LIABILITIES
Derivative financial liabilities
Level 2 [Member] | Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale	588,309	509,223
Trading securities held in a Rabbi Trust
Total securities	588,309	509,223
Total Assets	602,683	523,040
LIABILITIES
Total Liabilities	14,109	13,647
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	270,248	234,751
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	94,604	63,774
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	46,389	48,669
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	39,920	39,052
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale	128,313	114,264
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	8,835	8,713
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets	14,082	13,698
LIABILITIES
Derivative financial liabilities	14,050	13,647
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets	292	85
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets	0	34
LIABILITIES
Derivative financial liabilities	59
Level 3 [Member] | Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale
Trading securities held in a Rabbi Trust
Total securities
Total Assets
LIABILITIES
Total Liabilities	0
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets
LIABILITIES
Derivative financial liabilities
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets	0
LIABILITIES
Derivative financial liabilities